JPH01208531A - Air member for air flow control valve for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve air flow measuring accuracy by providing the sensor portion of an electric flow meter in a sub air flow passage and also devising the arranging position of the discharge port of a sub air flow passage, in the air meter in the caption which decides the sub air flow passage in an upper stream side air passage of the primary side and the secondary side valves. CONSTITUTION:A housing portion 7 constructing a sub passage containing a heating resistor hot wire 1 is installed in a main passage consisting of two bore passages having the primary side and the secondary side valves 5, 6. The hot wire 1 is constructed by winding platinum coil on e.g., an alumina body and coating its surface with glass materials and its both ends are welded to a pair of holding pins inserted in a mold case 3. The cold wire 2 of a resistor for temperature correction which detects on intake air temperature is constructed in a some manner as the hot wire 1 and it is installed together with the hot wire 1 in the sub passage portion in a housing 7. The discharge port 8 is opened toward the upper stream side of the secondary valve 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air flow meter for an air flow control valve (so-called throttle valve) provided in the middle of a combustion air intake pipe of an internal combustion engine, and particularly , relates to an air flow meter suitable for a two-bore type air flow control valve in which two valves are provided in parallel.

[Conventional technology]

In the conventional two-bore type hot-wire air flowmeter for internal combustion engines, the heating resistor was installed in the center of the main intake passage, as described in Utility Model No. 12836/1983. However, no consideration was given to the fact that the flow velocity distribution changes due to the influence of the opening degrees of the throttle valves on the primary side and the secondary side, and the appearance characteristics of the heating resistor change.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, in a two-bore type hot wire air flow meter, no consideration was given to the position of the outlet of the auxiliary flow path section consisting of the heating resistor and the housing, and the primary side valve of the throttle valve and the Depending on how the side valve opens, negative pressure is generated upstream of the secondary valve, increasing the flow rate coefficient, creating a pressure difference between the upstream side of the primary valve and the upstream side of the secondary valve, and increasing the flow rate. There was a problem in that the output characteristics changed due to the change in the output characteristics.

An object of the present invention is to provide an air flow meter for an internal combustion engine that is not affected by the throttle valve opening and has improved measurement accuracy.

[Means to solve the problem]

The above object is achieved by configuring the flow path outlet portion of the housing forming the intake air passage of the auxiliary flow path to blow air to the upstream side of the two-bore secondary throttle valve.

[Effect]

Blowing out the flow path outlet of the housing upstream of the 2-bore secondary throttle valve means that negative pressure is generated upstream of the secondary valve depending on the throttle valve opening, which increases the flow coefficient (air resistance). This means that the outlet of the auxiliary flow path is installed at a possible location where the flow rate becomes large.

For convenience of explanation, consider the following three states.

(i) Touch point state where the primary side valve is open and the secondary side valve is closed.

(it) Half open state Both the primary and secondary valves are half open.

(ni) Fully open state Both the primary and secondary valves are fully open.

Next, considering the touch point based on the fully open state, according to the above means (means taken to solve the problem), 1
Only the downstream valve opens, and even with the same suction flow rate, the main flow rate becomes faster because the outlet of the main flow path for the suction flow rate is narrower. It does not change because it flows through air resistance.

Next, even in the half-open state, similar to the touch point described above,
The negative pressure upstream of the secondary valve is greater than the negative pressure upstream of the primary valve, and the intake air flow rate in the sub flow path flows through the air resistance upstream of the secondary valve, and the flow rate does not change. . Due to the above operation, there is no malfunction of the output characteristics due to the influence of the throttle valve opening degree.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

Figure 1 shows a primary valve 5 and a secondary valve 6 in the main flow path.
FIG. 2 is a diagram schematically showing a hot wire air flowmeter in which a housing part 7 constituting a sub-flow path containing a heating resistor hot wire 1 is installed in a two-bore flow path having two throttle valves; FIG. 1 is a sectional view taken along the plane ■--■ shown in FIG.

In FIG. 1, a heating resistor hot wire 1 that senses the flow rate of an intake air flow 9 is made by winding platinum wire around an alumina bobbin and coating the surface with a glass material. Both ends of this hot wire 1 are molded. Each is welded to a pair of support pins (not shown) inserted into the case 3.

The cold wire 2, which is a temperature correction resistor for sensing the intake air temperature, also has the same structure as the hot wire 1. The molded case 3 to which the hot wire 1 and the cold wire 2 having such a structure are attached is attached to a body 4 comprising a main channel 10 through which intake air 9 flows and a housing section 7 forming a sub-channel section. Ru. Or hot wire 1
, the cold wire 2 is installed in a sub-flow path section within the housing section 7.

A current is applied to the hot wire 1 installed in the sub-channel to heat it to a constant temperature. This heating temperature is
Regardless of the amount of intake air 9, the difference between the hot wire temperature and the air temperature is kept constant, and the air temperature is corrected by the cold wire 2.

Therefore, when a high flow rate flows through the auxiliary flow path in the housing section 7, the hot wire 1 applies a high current, and when a low flow rate flows through the auxiliary flow path, a low current flows through the hot wire 1 to maintain a constant temperature. be. Between the current flowing through the hot wire 1 and the air flow rate,
There is a relationship of a monotonically increasing function, and the flow rate is detected based on this relationship.

The present invention relates to the installation position of the flow path outlet 8 of the housing portion 7 constituting the sub flow path in this hot wire air flowmeter. That is, in a two-bore type body 4 having a primary valve 5 and a secondary valve 6, the primary valve 5.
Influenced by the valve opening state of the secondary valve 6, negative pressure is generated upstream of the secondary valve 6, the flow coefficient (air resistance) increases, and the flow rate between the upstream of the secondary valve 6 and the primary valve 5 increases. A pressure difference occurs between the upstream and the upstream, and the flow velocity distribution in the main flow path lo changes.

In the conventional example, since no consideration was given to the influence of the valve opening state on the flow path outlet of the hot wire 1, as shown in FIG.
The problem was that the output characteristics were greatly disturbed.

In this embodiment, the flow path outlet 8 of the housing part 7 having the sub flow path provided with the hot wire 1 is installed on the secondary valve side 6, and the primary valve 5 and the secondary valve 6 are opened and closed. The condition is
At the touch point when only the primary side valve 5 is open, even if both valves are in a half-open state, the output characteristics are not affected by the valve opening degree based on the fully open state of both valves.

At the touch point, only the primary side valve 5 opens, so even if the intake air flow rate (9) is the same, the main flow path outlet part of the intake flow rate is narrow, so the flow speed in the main flow path becomes faster, but the hot wire 1 is arranged. The flow velocity in the sub flow path does not change because the flow passes through the air resistance of the negative pressure generated upstream of the secondary valve 6, and exhibits the same output characteristics as when both valves are fully open. Even when both valves are half open, the negative pressure upstream of the secondary valve 6 is 1
The intake air in the auxiliary flow path flows through the air resistance upstream of the secondary side, which is larger than the negative pressure upstream of the downstream valve 5, and does not affect the output characteristics, resulting in the characteristics shown in FIG. 4.

From the above, the flowmeter of this example is not affected by the open/closed state of the throttle valve, the output characteristics are stable, and the measurement accuracy is greatly improved.

[Effects of the Invention] According to the present invention, the influence of the two-bore throttle valve opening state can be reduced by installing the flow path outlet of the sub-flow path in which the air flow sensor is disposed on the secondary side throttle valve side. This has the practical effect of configuring a hot wire air flow meter with stable output characteristics and greatly improved measurement accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of a hot wire air flowmeter according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line ■--■ in FIG. 1. FIG. 3 is a chart of output changes in a conventional valve. FIG. 4 is an output change chart in the above embodiment. 1...Hot wire, 2...Cold wire, 3.
...Mold case, 4...Body, 5...Primary side valve. 6...Secondary side valve, 7...Housing part, 8...
- Channel outlet, 9... Intake air, 10... Main channel. Figure 1 Figure 2

Claims (1)

[Claims] 1. (a) A primary valve that adjusts the intake air flow rate when the internal combustion engine requires a small amount of air, and (b) operates when the internal combustion engine requires a large amount of air. and (c) a sub-air flow path that partitions a part of the air flow path on the upstream side of both of the above-mentioned valves. In the flowmeter, (d) a sensor portion of an electric flowmeter is provided in the auxiliary air flow path, and (e) the outlet of the auxiliary air flow path is directed toward the upstream side of the secondary valve. An air flow meter for an air flow control valve of an internal combustion engine, characterized in that it has an open opening. 2. The air flow meter for an air flow control valve of an internal combustion engine as set forth in claim 1, wherein the sensor portion (d) is a hot wire of a hot wire flow meter.